Abstract: A soft decision decoding method in a multiple-input multiple-output system which respectively receives two simultaneously transmitted data streams, a first transmitting symbol and a second transmitting symbol, in a first receiving signal and a second receiving signal is provided.

Abstract: In a method for estimating a signal-to-noise ratio (SNR) of an orthogonal frequency division multiplexing (OFDM) wireless mobile communication system, noise is estimated from adjacent received signals of at least two adjacent subcarriers and received signals of subcarriers, noise power is calculated by calculating a mean square value of the estimated noise by summing squares of the estimated noise, a mean square value of the received signals is calculated by summing squares of the received signals, signal power is calculated by subtracting the noise power from the mean square value of the received signals, and the SNR is calculated using the signal power and the noise power. Thus, the method of the present invention having low complexity can estimate an SNR efficiently regardless of channel changes on a frequency axis when one OFDM symbol includes preamble data.

Abstract: A method of determining a variable quantization step size is disclosed. In the method of determining a variable quantization step size, a channel characteristic parameter is obtained in order to calculate a quantization step size (?) used in channel decoding. The quantization step size (?) is variably determined based on the channel characteristic parameter. Therefore, the method of determining a variable quantization step size may improve channel decoding.

Abstract: A filter tuning system for quickly compensating a time constant using a binary search algorithm is disclosed. The filter tuning system includes a time constant detector, a comparator and a calibration unit. The time constant detector detects a time constant of a filter based on an integral value of a reference input signal using an integrator when the time constant of the filter changes according to a variation of a manufacturing process or a temperature. The integrator includes a capacitor changing according to a variation of the time constant of the filter. The comparator compares the detected time constant with a reference value. The calibration unit compensates the time constant of the filter using the binary search algorithm based on the comparison result until an error between the time constant and the reference value is reduced within an acceptable range.

Abstract: A Doherty amplifier is provided. The Doherty amplifier includes a first path circuit including a carrier amplifier and a first impedance adjusting circuit connected with the carrier amplifier; and a second path circuit including a peaking amplifier, a second impedance adjusting circuit connected with the peaking amplifier, and a peaking amplifier bias circuit connected with the peaking amplifier. At least one among an impedance of the first impedance adjusting circuit, an impedance of the second impedance adjusting circuit, and a bias of the peaking amplifier bias circuit is adjusted in response to a control signal.

Abstract: An orthogonal frequency division multiplexing (OFDM) system and a method of controlling preamble power of the OFDM system are provided. The method includes detecting a present preamble power of a certain base station among a plurality of base stations and a preamble influence factor of the certain base station; detecting a preamble influence factor of at least one neighboring base station of the certain base station; and determining a new preamble power of the certain base station based on at least one among the present preamble power, the preamble influence factor of the certain base station, and the preamble influence factor of the at least one neighboring base station.

Abstract: An orthogonal frequency division multiplexing (OFDM) system and an inter-cell interference cancelling method performed in the OFDM system are provided. The OFDM system includes a Fourier transformer which transforms a received base band signal into a pilot subcarrier signal and a data subcarrier signal, a Doppler/delay spread estimator which estimates a coherent time and a coherent bandwidth from the pilot subcarrier signal, a pilot block size selector which selects a pilot block including at least one pilot signal, based on the coherent time and the coherent bandwidth, a simultaneous channel estimator which estimates a channel response signal based on the at least one pilot signal located in the pilot block, and a simultaneous symbol extractor which extracts a data symbol from the data subcarrier signal on the basis of the channel response signal.

Abstract: A soft decision decoding method in a multiple-input multiple-output system which respectively receives two simultaneously transmitted data streams, a first transmitting symbol and a second transmitting symbol, in a first receiving signal and a second receiving signal is provided.

Abstract: A Doherty amplifier is provided. The Doherty amplifier includes a first path circuit including a carrier amplifier and a first impedance adjusting circuit connected with the carrier amplifier; and a second path circuit including a peaking amplifier, a second impedance adjusting circuit connected with the peaking amplifier, and a peaking amplifier bias circuit connected with the peaking amplifier. At least one among an impedance of the first impedance adjusting circuit, an impedance of the second impedance adjusting circuit, and a bias of the peaking amplifier bias circuit is adjusted in response to a control signal.